This invention relates generally to optical power measuring apparatus, and more particularly to a method and apparatus for measuring the average power in an intense optical beam, typically but not restricted to a laser beam.
The two most commonly used methods of measuring the power level in an optical beam are, first directing the beam onto a device whose response to the beam is known and secondly diverting a portion of the beam onto such a device. The principal disadvantages which limit the usefulness of these two methods is that the average level of power remaining in the transmitted beam is undesirably reduced as a consequence of making the measurement. If the beam is diverted from its intended target to make a measurement, the time average of the power directed toward the target will be less than the maximum available from the system, even though full power may be directed toward the target most of the time. In the same manner, if a portion of the power available in the optical beam is continuously diverted to a measuring device, the time average of the power directed to the target will be less than the peak available power from the system.